Method and arrangement for measuring the resistance ratio in a

Abstract

The measuring circuit is used to measure the resistance ratio .DELTA.R/R in a resistance half-bridge comprising two series-connected resistors, of which the one resistor has the resistance R+.DELTA.R and the other resistor the resistance R-.DELTA.R. The two resistances are traversed by the same current which generates a voltage drop at each resistor. By an integrating SC amplifier in successive sampling cycles difference voltages which are proportional to the difference between the voltage drops at the two resistors are integrated to give an integration voltage. Every time the integration voltage exceeds an upper threshold value or drops below a lower threshold value in a compensation cycle a compensation voltage directed oppositely to the difference voltage is superimposed on the integration voltage and is proportional to the sum of the voltage drops at the two resistors. As a measure of the resistance ratio .DELTA.R/R the ratio of the number of compensation cycles to the number of sampling cycles is determined in that the compensation cycles are counted in a time window corresponding to a predetermined number of sampling cycles. The count indicated then directly represents in a corresponding scale the desired resistance ratio .DELTA.R/R.